1. Field of the Invention
This invention relates generally to a system and method for updating map databases used in mobile computer-based applications and, more particularly, to a system and method for incrementally updating a map database used in a vehicle navigation system that includes computation of the changes between the latest version of a master map database and a previous version of the map database, transmission of those changes to participating vehicles' onboard navigation systems, and using those changes with a base onboard map database for navigation purposes.
2. Discussion of the Related Art
Many modern mobile computing applications rely on an accurate road map database to perform their functions. One of the most common such applications is an onboard vehicle navigation system, but there are others, such as active vehicle safety systems and driver assistance systems. These mobile computing applications are delivered to the consumer pre-loaded with a current map database. However, changes to the map data are inevitable as roads are added or changed, intersections are added or modified, temporary road closures and detours are implemented, data errors are discovered and corrected, new points of interest arise, and so forth. The need exists for an efficient way of updating the mobile map databases to reflect these changes; without such updates, the mobile map databases will become increasingly inaccurate over time, as changes to the road system accumulate.
Updating the map database in many thousands or millions of mobile computing systems is typically problematic. One method of doing so is to automatically download a complete new database to the mobile computing systems periodically. This approach is prohibitively slow, because the bandwidth for wireless transmission is low and the size of the databases is large. An alternative is to send out a physical computer disk (CD or DVD) to the owners of all applicable mobile computing systems and ask the owners to install the new database. This approach is costly and unreliable.
Another alternative is to automatically download just the incremental changes of the map database to the participating mobile computing systems periodically. This approach has the advantages of being automatic and minimizing wireless bandwidth consumption. But until now, the efficient real-time usage of the change data in conjunction with the base map data has not been possible. The identification reference numbers of road segments and intersections often change from one version of a master map database to the next version, so it is not possible to simply merge the changes with the baseline map data in the mobile device. Another reason a simple merge is not possible is because the map databases are heavily indexed—by geography, connectivity, and so forth—to improve search performance, so if new data were inserted the entire database would have to be re-indexed. Further, such re-indexing is not practical in typical mobile computing devices, such as vehicle navigation systems, because those systems do not have the computational power necessary for the task. In order to make possible the use of incremental map change data in mobile computing devices, a new methodology of storing the changes and re-integrating them in real time with the base map data is needed.